This invention relates generally to an electrophotographic printing machine, and more particularly concerns an improved paddle wheel substrate feeding system for feeding substrates, which term is used herein to include sheets of any type, from a stack of sheets along a predetermined path.
Many of the prior sheet feeding mechanisms occasionally malfunction, feeding more than one sheet at a time or failing to feed on demand. Consistent feeding is often difficult to achieve with different stack heights. Complex elevator devices are often employed with some success to maintain the top of stack of sheets at a uniform height.
Presently, many paper handling applications in copiers use elastomeric paddle wheels. Among these are feeders and restack registration where paddle blade deflections vary over several millimeters as sheets are removed or added to the system. In a feeder application, this means that variations in stack height due to stack height sensor differentials and elevator overrun will not cause unacceptable variations in normal force. As a result there is a need for low blade normal force sensitivity to deflection or penetration against the sheet being fed to enhance individual feeding of sheets. In addition, since paddle wheels are elastomeric friction devices, increasing friction and reducing the wear rate of paddle wheels are achievable in many cases by reducing paddle blade contact pressure.